Common use of 3(a) Clause in Contracts

3(a). In the short term, selection for an increase in development time can be (as seen for SLOW) associated with an increase in pupal weight, but after the intermediate maximum, pupal weight will decrease with increasing larval time. Possibly the first, ascending part of the curve represents a trade-off, whilst the latter, descending phase is more a result of environmental variables. The parabolic relationship would suggest that obtaining a longer development period in the long term can only be achieved by decreasing growth rate, and will be associated with a decrease in pupal weight. However, the interaction between the quadratic larval time component and selection line points to the fact that the development time - weight relation could change for SLOW selected lines (compare the curvature of the selection lines in figure 7.3a, the SLOW line is much flatter). FAST lines achieved their faster development via a higher growth rate, but had equal pupal weight to FMSF and SMFF lines. Presumably, this higher growth rate has come at a cost in terms of some other component of fitness (▇▇▇▇▇, 1994). Alternatively, the protandry selection lines may have decreased pupal weights because their genetic architecture has been disrupted. The change in growth rate accounting for the changes in development time, and the non-linear relationship between larval time and pupal weight underline the importance of growth rate in life-history evolution. The straightforward time - weight trade-off which is often assumed would in this case lead to erroneous conclusions. Conclusions about trade-offs and in particular with respect to protandry, are further complicated by the fact that fertility and fecundity do not relate in a straightforward fashion to development time and body size (chapter 6). In figure 7.6, the relationships between development time, pupal weight, and growth rate (inverted for easier comparison) are shown conceptually within and across sexes. In theory, all connections in this figure can vary under specific circumstances, but the important connection with regard to protandry is the line connecting male and female development time (the line between the two apexes). We have been unable to change this relationship (chapter 6), which may perhaps arise as a result of changes in other connections between life-history traits across the sexes (assuming constancy of the triangle within one sex). For example, selection for a decreased amount of protandry, that is, for slow males and fast females, might not have yielded a response because of changes in growth rate or pupal weight (visualised as the dotted triangles). However, the protandry selected lines showed intermediate growth rates and pupal weights that did not differ from patterns expected for stock animals. This refutes the hypothesis that changes in protandry are buffered by changes in either growth rate or pupal weight (see below). In other words, the absence of a response to selection for protandry cannot be accounted for by changes in pupal weight and/or growth rate.